1. Technical Field
This invention generally relates to removable paddle shaft assemblies for mixing machines such as mortar mixers, and in particular it relates to a removable paddle shaft assembly which does not require any disassembly of the mixer for removal and reinstallation of the paddle shaft assembly.
2. Background Art
Mixing machines, such as mortar mixers and the like, generally have a horizontally disposed cylindrical drum including an opening along its top side and a paddle shaft assembly being coaxially and rotationally secured within the drum which includes a plurality of radially extending mixing paddles. A drive means is provided for rotationally driving the paddle shaft assembly to facilitate mixing of the contents in the mixing drum. The mixing drum is pivotally secured to a mixer frame via a pair of double actioned bearing assemblies. The bearing assemblies allow the drum to be radially displaced between an upright mixing position and an angular dumping position without interfering with the rotation of the paddle shaft assembly. A hinged grate covers the top opening as a safety precaution to prevent foreign objects form entering the mixing drum while mixing.
Because of the abrasive environment inside the mixing drum, the mixing paddles wear quickly and consequently must be replaced frequently. Presently, this is accomplished by a service technician or mechanic in a repair shop, due to the complexity of the bearing assemblies and the fact that the mixing drum must be dissassembled. Mortar mixers receive very little, if any, in field service. The service which is accomplished in the field is usually done with a hammer in a haphazard manner. This is simply a consequence of the construction environment.
Because of the environment in which mortar mixers are used and the reluctance of construction workers to properly service mortar mixers, the mixers spend a great deal of time in the shop being serviced and having worn parts replaced. The ideal mortar mixer would be one which requires very little maintenance and one in which the maintenance which is required could be performed in the field by a construction worker armed only with a hammer, since this seems to be the tool of choice.
FACE, JR., U.S. Pat. No. 4,097,926 teaches a mortar mixer having a removable paddle shaft assembly which can be removed without major disassembly of the bearings, or mixing drum. Face, Jr. uses a specialized bearing assembly on one end which includes a through sleeve for receiving a quill shaft. The quill shaft extends coaxially through the mixing drum, engaging a hollow paddle shaft, and is coupled to a drive shaft at a first end. The second end of the quill shaft includes a flange member which is subsequently attached to a flange on the receiving sleeve. To remove the hollow paddle shaft, one has to decouple the quill shaft flange from the receiving sleeve flange and withdraw the quill shaft from the drum. This disengages the quill shaft with the hollow paddle shaft and the paddle shaft can then be removed out the top opening of the mixing drum and a new paddle shaft can be reinstalled. Besides requiring a non-preferred bearing assembly, this paddle shaft assembly requires the use of a screw driver or wrench for removal, neither of which are the construction worker's tool of choice. Additionally, in order to be able to withdraw the quill shaft, it must be kept free from dried mortar which readily adheres to the metal surfaces. This requires thorough and frequent cleaning of the paddle shaft assembly which is rarely done.
What is needed is a removable paddle shaft assembly which does not require disassembly of the bearing assemblies or mortar mixer drum, wherein removal and reinstallation of the paddle shaft assembly can be accomplished using only a hammer.
Accordingly, it is an object of this invention to provide an easily replaceable paddle shaft assembly which can be removed and reinstalled having access to only the interior of the drum without any disassembly of the bearings or mixer drum using only a hammer.